Field of the Invention
The present invention relates to a radiation imaging apparatus.
Description of the Related Art
As a radiation imaging apparatus which captures an image of radiation such as X-rays, a radiation imaging apparatus with a radiation imaging panel where conversion elements which convert radiation into charges are arrayed two-dimensionally is known. Some conversion elements convert radiation into visible light and then convert this visible light into the charges, or convert radiation into the charges directly. Each conversion element includes a semiconductor layer. A dark current generated in this semiconductor layer becomes an offset component to cause shading.
Japanese Patent Laid-Open No. 2011-223088 has described an imaging apparatus which corrects, based on a dark signal amount by a dark current, charge information at the time of radiation irradiation. The imaging apparatus described in Japanese Patent Laid-Open No. 2011-223088 includes a plurality of temperature sensors on the periphery of a conversion layer which converts information on light or radiation into charge information and measures a temperature distribution by these sensors. When capturing a radiation image, a dark signal amount is obtained based on the correlation between the temperature distribution and the dark signal amount stored in advance and the temperature distribution obtained by using the plurality of temperature sensors, and the charge information is corrected based on this dark signal amount. In a method described in Japanese Patent Laid-Open No. 2011-223088, correction is made based on the correlation between the temperature distribution and the dark signal amount stored in advance, and the temperature distribution measured when capturing the radiation image. Therefore, the temperature sensors and a memory which stores the correlation are indispensable, complicating an arrangement. In the method, a dark signal amount is not actually measured at the time of image capturing. As a result, a deviation may occur between the dark signal amount obtained based on the correlation and the actual dark signal amount.
A radiation imaging apparatus having an exposure control function is also known. Japanese Patent Laid-Open No. 2012-247354 has described a radiation image detection apparatus which detects at least one of the start and the end of radiation irradiation. The radiation image detection apparatus includes an imaging region where a plurality of pixels are arrayed in a matrix and a plurality of detection elements which output electrical signals corresponding to the incident amount of radiation. The radiation image detection apparatus detects at least one of the start and the end of radiation irradiation based on the output of a detection element having a high sensitivity out of the plurality of detection elements.
Note that a technique of correcting a radiation image based on information obtained by a detection element or sensor for exposure control is not known.